(1) Field of the Invention
The present invention relates to an apparatus for setting image processing conditions in scanning and recording documents with an image scanning and record-recording apparatus such as a prepress scanner. More particularly, the invention relates to an apparatus for setting image processing conditions, which is constructed separately from the image scanning and recording apparatus.
(2) Description of the Related Art
In scanning and recording a document with a prepress scanner, for example, density levels (normally in dot %) of selected positions, e.g. such as highlight points and shadow points, of the document are set as image processing conditions (hereinafter referred to as "setup") in advance in order to reproduce the document in a desired state.
An ordinary prepress scanner has such a setup function. FIG. 1 illustrates an outline of the setup function which the prepress scanner possesses.
In FIG. 1, light transmitted through or reflected by document F mounted on a rotary cylinder 1 travels through a pickup lens 2 and to a total reflection mirror 3 pivotable between an open position and a closed position. During a setup time the total reflection mirror 3 is opened to allow the light to travel to a viewer 4. The operator moves the rotary cylinder 1 and pickup lens 2 while watching the documents F through the viewer 4, to select appropriate positions as hightlight points or shadow points (here-inafter referred to as setup positions).
After setup positions are selected, the total reflection mirror 3 is set to the closed position. Then the light is reflected to the mirror 3 to travel through an aperture 5 and enter a color separating optical system 6 including a red reflection dichroic mirror 6a, a blue reflection dichroic mirror 6b, and a total reflection mirror 6c. Color components of red (R), green (G) and blue (B) emerging from the color separating optical system are converted into electric signals by photomultipliers 7a, 7b and 7c, respectively, which are inputted to a computing circuit 8. The computing circuit 8 converts the R, G and B signals into yellow (Y), magenta (M), cyan (C) and black (K) color signals. These color signals are converted into density levels (normally dot %) and shown on a density indicator 9. The operator views the density levels of the respective color signals shown on the density indicator 9, and judges whether the selected setup positions are appropriate or not. If the selected positions are found appropriate, the operator inputs desired density levels of these positions through a keyboard 10. The input density levels are set to the computing circuit 8 as image processing conditions, which completes the setup operation.
Conventionally, the setup operation by means of the scanner as described above is followed by scanning and recording of the document with the same scanner. Otherwise the scanner is used exclusively for the setup purpose, document reading and recording being carried out with a different scanner. In the former, the document cannot be read or recorded during the setup operation, resulting in a low operating rate of the scanner. The latter requires a plurality of expensive prepress scanners, which is a disadvantage from the cost point of view.
Under the circumstances, apparatus intended specially for setup have been proposed, which are of separate entity from the prepress scanner and which are relatively inexpensive and yet have good operability although not attaining as high precision as the prepress scanner does (see Japanese Patent Laying-Open Publication No. 62-231566, for example). In this specification, such a setup dedicated apparatus is called an image processing condition setting apparatus.
As shown in FIG. 2, an image processing condition setting apparatus comprises a chuck 11 rotatably supporting a rotary cylinder 1 carrying a document, and a viewer 12 slidable along a rotation axis of the chuck 11. The chuck 11 and viewer 12 have position detectors, not shown, for detecting positions thereof. respectively. As shown in FIG. 3, the viewer 12 includes a light source 13, a condenser lens 14, a mask 15 defining a register cross M, a projecting lens 16, a half mirror 17 and a lens 18. The register cross M drawn of the mask 15 is projected to the document F to enable visual confirmation of setup positions.
The operator sets the register cross M to a setup position by rotating the cylinder 1 (and chuck 11) and sliding the viewer 12, and inputs a desired density level of that position through a keyboard 19. The input density level is recorded, along with position data of that position as detected by the position detectors, on a floppy disk inserted into a disk drive 20 or other storage medium.
After necessary image processing conditions are written into the floppy disk, the latter is set to the prepress scanner. In this way, the image processing conditions set by the image processing condition setting apparatus are retrieved by the prepress scanner.
The setup positions on the document F are selected by the operator based on his or her experience. It is desirable to determine whether the selected setup positions are actually suitable as highlight points or shadow points or not, by referring to density levels of the color components of those positions. This is because, if a position selected as a highlight point, for example, shows an imbalance of color, that position is inappropriate as a highlight point, and its use would mar the image quality of a printout.
With the known apparatus illustrated in FIG. 2, however, the density level of a selected position cannot be confirmed. After a setup operation by this apparatus, the prepress scanner is operated to measure the density level of that position for checking if that position is appropriate as a setup position. If inappropriate, a setup operation must be carried out with the prepress scanner all over again.
Besides, as noted with reference to FIG. 1, an attempt to check the density levels of a plurality of positions on a document with the conventional prepress scanner involves the trouble of manually opening and closing the total reflection mirror 3 every now and again. Such an operation is time-consuming and unfavorable for the efficiency of the prepress process.
In the prepress scanner schematically shown in FIG. 1, the total reflection mirror 3 must be opened and closed for confirming the density level of a highlight point or the like as one step of the setup operation for the following reason:
In the prepress scanner, generally, the size of aperture 5 which determines a document input range in the color separating optical system 6 is varied with image processing (reproducing) magnification. Particularly when the magnification is at a high ratio, the size of aperture 5 is reduced to the order of 0.1 mm in diameter. As a result, minimal light intensity is applied through the color separating optical system 6 to the photomultipliers 7a-7c. Because of the limitation to the light sensitivity of these photomultipliers 7a-7c, the light cannot be led simultaneously to the viewer 4 and to the color separating optical system 6. As a consequence, the total reflection mirror 3 must be used to switch the optical path.
In addition, since the total reflection mirror 3 is switched between the open and closed positions, the operator often fails to notice a slight movement of the document-carrying cylinder or scanning head occuring before or after a switching operation. This results in a shift between an input range observed through the viewer 4 and an output range for which the density is actually measured. The staggered portions may have a density discrepancy, which will frustrate the operator in his attempt to correctly effect a desired setup.